JPH1169554A - Manufacture of insulating tape and power cable connection using the tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the strength and an extension magnification of a tape and also make it possible to wind the tape thin by a method wherein an additional cross linking agent is added after an uncrosslinked sheet or tape including a cross linking agent which is necessary for obtaining a required mechanical characteristic is crosslinked. SOLUTION: As for a method for manufacturing this insulating tape, an uncrosslinked sheet or tape including a crosslinking agent which is necessary for obtaining a mechanical characteristic required at the time of winding is shaped and crosslinked and then is dipped and impregnated and aged to obtain a semi-crosslinking agent-containing tape and then an additional crosslinking agent is added to this tape. As for the crosslinking agent preliminarily included in the sheet or tape, an organic peroxide crosslinking agent such as dicumyl peroxide, perhexa V, and perhexa 3M is used. For the additional crosslinking agent, the same type of crosslinking agent is used. By this method, the obtained tape has a higher green strength than an uncrosslinked tape and a variation in mechanical characteristic can be suppressed and the efficiency of a tape winding work can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an insulating tape for forming a reinforcing insulating layer formed on a connection portion of a power cable, and a power cable connection portion using the insulating tape.

[0002]

2. Description of the Related Art Some power cable connection methods use a tape to form a reinforcing insulating layer. The tape material used is polyethylene or ethylene-propylene rubber (EPDM), the same as the insulator of the power cable.
Rubber is mainly used. When polyethylene is used for the reinforcing insulator, the connection method includes TMJ (tape mold joint). The TMJ is wound and then molded. In the case of molding, a crosslinking agent is added to the tape in advance, and the tape is melted and crosslinked with the cable insulator to be integrated. In the case where EPDM is used for the reinforcing insulator, similarly to the TMJ, a tape containing a crosslinking agent is wound and then subjected to a molding treatment, the reinforcing insulator is crosslinked, and integrated with the cable insulator to form a connection portion. The tape used is an uncrosslinked tape to which a crosslinking agent has been added in advance. The method for producing such a tape containing a crosslinking agent is as follows. In the case of a polyethylene tape, a pellet containing a crosslinking agent obtained by adding a crosslinking agent to a material pellet is formed into a sheet shape using a molding machine such as an extruder, and then the tape is formed by cutting. Often do. In the case of rubber, a cross-linking agent is added at the time of kneading as in the case of other additives, and a tape is often formed by cutting and then forming a sheet using a molding machine such as a calender roll or a roller head extruder.

[0003]

SUMMARY OF THE INVENTION Among uncrosslinked tapes,
In particular, amorphous rubber materials such as ethylene-propylene rubber generally have lower mechanical strength (green strength) in an uncrosslinked state than semi-crystalline plastic materials such as polyethylene. When performing tape winding, it is difficult to wind with an excessively high tension or to increase the stretching ratio. When a tape is wound on the reinforcing insulating layer of the power cable connection portion, it is desirable that the stretching ratio be increased as much as possible and the tape be thinly wound. When winding tapes, the tapes are usually wrapped together. Then, the end in the width direction of the tape becomes a step, and a gap is generated between the tape and the tape to be wound up. The effect of increasing the draw ratio is to make the gap as small as possible by utilizing the tensile strength of the tape.
Also, by increasing the stretching ratio, the stretched tape becomes thinner and the step of the lap becomes smaller, so that the gap becomes smaller. The use of a tape as thin as possible is also due to the latter reason.

Therefore, as a method of increasing the green strength, an uncrosslinked tape to which a crosslinking agent has been added is pressurized and heated.
Use of a semi-cross-linked tape cross-linked by a part of the added cross-linking agent is considered. However, with a semi-cross-linked tape made by such a method, it is difficult to control a cross-linking reaction, and thus it is difficult to obtain a stable green strength.

[0005] The present invention provides a method of manufacturing an insulating tape which can improve the strength of the tape, increase the draw ratio, and enable thin winding.
It is an object of the present invention to provide a power cable connecting portion in which the working efficiency is improved by using the insulating tape, the gap between the tape and the tape to be wound up is reduced as much as possible, and the withstand voltage characteristic is improved.

[0006]

In order to achieve the above object, the present invention relates to a manufacturing method of an insulating tape for forming a reinforcing insulating layer formed at a connection portion of a power cable. A step of forming an uncrosslinked sheet or tape containing the crosslinking agent necessary to obtain the sometimes required mechanical properties; a step of crosslinking the uncrosslinked sheet or tape; Adding a suitable crosslinking agent. Further, the invention relating to the power cable connection portion electrically connects both cable conductors of the power cable, wraps the connection portion with the insulating tape manufactured by the above-described manufacturing method, and heats the wrapped insulating tape. To form a reinforcing insulating layer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing an insulating tape according to the present invention comprises forming an uncrosslinked sheet or tape containing a crosslinking agent necessary for obtaining the required mechanical properties at the time of winding the tape, and then crosslinking the tape. Next, a new cross-linking agent is made into a liquid or gaseous state, immersed in a sheet or tape, impregnated and aged to obtain a tape containing a semi-cross-linking agent. As a crosslinking agent previously contained in the sheet or tape, dicumyl peroxide (DCP), Perhexa V, Perhexa 3M, etc., which are organic peroxide crosslinking agents, are preferably used. The same thing is suitably used as a new crosslinking agent.

[0008] There is no limitation on the method of processing a sheet or tape containing such a crosslinking agent. From a material containing a crosslinking agent in advance, sheet molding and subsequent tape molding may be performed. Alternatively, a material containing no crosslinking agent may be formed into a sheet, and the crosslinking agent may be added in a sheet state, or the crosslinking agent may be added after tape processing. There is no difference in characteristics due to any of the processing methods. The method of adding the crosslinking agent after the sheet or tape is formed is not particularly limited, and examples thereof include the following method. (a) Prepare a bath of a liquid cross-linking agent (for a solid at room temperature, use a melt having a melting point or higher), pass through the bath over a certain period of time, and impregnate a certain amount of the cross-linking agent. The amount of the cross-linking agent impregnated is controlled by temperature and time. (b) Impregnating a certain amount of cross-linking agent by a technique such as coating or printing. Subsequently, the impregnated crosslinking agent needs to be evenly dispersed within the tape. Although there is no particular limitation on the dispersing method, there is, for example, the following method. That is, there is a method in which the crosslinking agent is stored in a place where the temperature is controlled for a certain period of time to diffuse the crosslinking agent from the tape surface to the inside.

The sheet or tape containing a cross-linking agent obtained as described above is subjected to tape processing in the case of a sheet to obtain an uncross-linked tape. The uncrosslinked tape thus obtained contains a crosslinking agent that satisfies the mechanical properties required when winding the tape after crosslinking, and is crosslinked.

[0010] The crosslinking method is not limited, but when a crosslinking agent such as a peroxide crosslinking agent that generates a gas is used in the crosslinking step, the gas generated by the reaction causes the tape to foam, It is conceivable that voids are generated in In such a case, crosslinking under an appropriate pressurized environment is required. The pressurized atmosphere is not particularly limited, and may be, for example, steam pressurization, nitrogen pressurization, or pressurization using a liquid (silicone oil, insulating oil, or the like). The process may be a batch process such as a pressure cooker, or a method of passing continuously under a pressurized environment such as a pressurized cylinder over a certain period of time to perform continuous crosslinking.

A new cross-linking agent is added to a sheet or tape obtained by cross-linking a sheet or tape containing only a cross-linking agent satisfying the mechanical properties. As a method of addition, the sheet or tape is immersed in a liquid or gaseous crosslinking agent to be impregnated and aged. The semi-crosslinked insulating tape thus obtained always has a desired green strength and contains a crosslinking agent necessary for the subsequent crosslinking reaction.

Example 1 Additives other than a crosslinking agent were added to a base rubber (EPDM).
The mixture was kneaded, and immediately after kneading, a foreign material was screened with a predetermined mesh through an extruder. Thereafter, a crosslinking agent necessary for obtaining a desired green strength was added and kneaded, and a sheet was formed by a calender roll forming machine. The obtained sheet was put into a steam pressurized kettle, pressurized and heated, and crosslinked by the added crosslinking agent. The sheet is passed through a bath of a cross-linking agent, impregnated with the cross-linking agent, stored in a thermostatic layer for a predetermined time, uniformly diffused in the sheet, cut into a tape, and cut into a tape. A crosslinked ethylene-propylene rubber tape was produced.

Example 2 Additives other than a crosslinking agent were added to a base rubber (EPDM).
The mixture was kneaded, and immediately after kneading, a foreign material was screened with a predetermined mesh through an extruder. Thereafter, the sheet was formed by a calender roll forming machine, the sheet was passed through a bath of a cross-linking agent, impregnated with the cross-linking agent, stored in a thermostatic layer for a predetermined time, and the cross-linking agent was uniformly diffused in the sheet. . The obtained sheet was put into a steam pressurized kettle, pressurized and heated, and crosslinked by the added crosslinking agent. The sheet is passed through a bath of a cross-linking agent, impregnated with the cross-linking agent, stored in a thermostatic layer for a predetermined time, uniformly diffused in the sheet, cut into a tape, and cut into a tape. A crosslinked ethylene-propylene rubber tape was produced.

Comparative Example 1 An additive other than a crosslinking agent was added to a base rubber (EPDM).
The mixture was kneaded, and immediately after kneading, a foreign material was screened with a predetermined mesh through an extruder. Thereafter, a crosslinking agent was added and kneaded, the sheet was formed by a calender roll forming machine, and then cut into a tape to produce a semi-crosslinked ethylene-propylene rubber tape containing a crosslinking agent.

Comparative Example 2 Additives other than the crosslinking agent were added to the base rubber (EPDM).
The mixture was kneaded, and immediately after kneading, a foreign material was screened with a predetermined mesh through an extruder. Thereafter, a crosslinking agent was added and kneaded, and a sheet was formed by a calender roll forming machine. The above-mentioned sheet is thrown into a steam pressurized kettle to give a heat history necessary for obtaining a desired green strength, then taken out, cut into a tape shape, and semi-crosslinked ethylene-containing a crosslinking agent.
Propylene rubber tape was manufactured.

In each of Examples 1 and 2 and Comparative Examples 1 and 2 described above, the average, maximum, and minimum values of the green strength of the semi-crosslinked sheet when 50 batches of tape having a thickness of 0.5 mm and a width of 25 mm were manufactured. The results of comparing the values (relative values when the average of Example 1 is 100) are as shown in Table 1 below.

[0017]

[Table 1]

As the evaluation of the high stretchability at the time of winding the tape, the maximum stretch ratio at which one roll of the tape can be wound without breaking at all and the thickness of the tape at that time were measured using a tape winding machine.
The results are as shown in Table 2 below. Note that the values in the table are relative values when Example 1 is set to 100.

[0019]

[Table 2]

FIG. 1 shows a state in which the insulating tape 1 manufactured as described above is wound around a connection portion where the two cable conductors 3 of the power cable 2 are electrically connected to each other. FIG. This shows a state in which the wound insulating tape 1 is heated and crosslinked, and further pressurized to form the reinforcing insulating layer 4. When an electric test was performed on the power cable connection portion on which such a reinforcing insulating layer 4 was formed, all the samples (the insulating tapes of Examples 1 and 2) passed the standard test.

[0021]

According to the present invention, a sheet or tape containing only a crosslinking agent necessary to obtain a desired green strength is crosslinked by an appropriate heat and pressure treatment, and then a new crosslinking agent is added to obtain a semi-crosslinked product. By manufacturing the tape, the green strength is improved as compared with the non-cross-linked tape, and it is possible to manufacture a semi-cross-linked tape with less variation in mechanical properties than before. In addition, the power cable connecting portion in which the reinforcing insulating layer is formed with such a semi-crosslinked insulating tape also improves the efficiency of the tape winding operation, has no gap between the tapes, and has good electric characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state when an insulating tape is wound.

FIG. 2 is a cross-sectional view of a power cable connection portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation tape 2 Power cable 3 Cable conductor 4 Reinforcement insulation layer

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 105: 24 B29L 7:00

Claims (2)

[Claims] 1. A method of manufacturing an insulating tape for forming a reinforcing insulating layer formed at a connection portion of a power cable, comprising a cross-linking agent necessary for obtaining mechanical properties required when winding the tape. Manufacturing an insulating tape, comprising: a step of forming a crosslinked sheet or tape; a step of crosslinking this uncrosslinked sheet or tape; and a step of adding a new crosslinking agent to the sheet or tape. Method. 2. An electrical connection between two cable conductors of a power cable, winding an insulating tape manufactured by the manufacturing method according to claim 1 around the connection portion, and heating and winding the wound insulating tape. And then further pressurized to form a power cable connection portion on which a reinforcing insulating layer is formed.